Rosilene Oliveira Mesquita

Integrative Control Between Proton Pumps and SOS1 Antiporters in Roots is Crucial for Maintaining Low Na+ Accumulation and Salt Tolerance in Ammonium-Supplied Sorghum bicolor

An effective strategy for re-establishing K+ and Na+ homeostasis is a challenge for the improvement of plant performance in saline soil. Specifically, attempts to understand the mechanisms of Na+ extrusion from plant cells, the control of Na+ loading in the xylem and the partitioning of the accumulated Na+ between different plant organs are ongoing. Our goal was to provide insight into how an external nitrogen source affects Na+ accumulation in Sorghum bicolor under saline conditions. The NH4+ supply improved the salt tolerance of the plant by restricting Na+ accumulation and improving the K+/Na+ homeostasis in shoots, which was consistent with the high activity and expression of Na+/H+ antiporters and proton pumps in the plasma membrane and vacuoles in the roots, resulting in low Na+ loading in the xylem. Conversely, although NO3--grown plants had exclusion and sequestration mechanisms for Na+, these responses were not sufficient to reduce Na+ accumulation. In conclusion, NH4+ acts as an efficient signal to activate co-ordinately responses involved in the regulation of Na+ homeostasis in sorghum plants under salt stress, which leads to salt tolerance.

Differential Impact of Acclimation and Acute Water Deprivation in the Expression of Key Transcription Factors in Soybean Roots

Soybean (Glycine max) is one of the major world commodities. In order to increase the soybean yields, it has been searched drought-tolerant cultivars, once the drought is the major constraint to soybean grown. Therefore, it is crucial to elucidate the molecular mechanisms associated with drought tolerance. Here, the in silico approach allowed us to identify 12 genes belonging to six different transcription factor families in soybean that have been associated with key events on drought response. The expression pattern of each gene was investigated by qPCR in root samples of drought-sensitive and drought-tolerant cultivars undergoing drought stress in pot-based (PSys) and hydroponic (HSys) cultivation systems. GmaxMYC2-like 2 was induced under abrupt drought conditions in HSys in both cultivars, whereas GmaxAREB1-like 1 and GmaxDREB2A-like were highly induced only in the PSys. However, GmaxMYB2-like 1, GmaxMYB2-like 2, GmaxRD26/NAC-like 1, GmaxRD26/NAC-like 2, GmaxAREB1-like 2, and GmaxDREB1A-like were upregulated in both systems, while the GmaxHB6-like and GmaxHB13-like are repressed under all of the investigated conditions. Exogenous abscisic acid (ABA) treatment was used to identify those genes belonging to the ABA-dependent drought response. The genes identified in this work have potential application for the improvement of drought resistance in soybean and markers for breeding programs.